Immunogenicity of highly purified bovine insulin: a comparison with conventional bovine and highly purified human insulins

Summary Twenty-six Type 1 diabetic patients previously treated for 10–20 months with twice daily conventional bovine isophane insulin (containing at least 1000 ppm proinsulin) were changed to highly purified (<1 ppm proinsulin) bovine isophane for 6 months (Switch group). Insulin antibody levels fell significantly from a geometric mean of 14.9 to 9.1 g/l. Thirty-two patients with newly diagnosed Type 1 diabetes were treated with the same highly purified bovine isophane insulin twice daily for 6 months (Starter group). Their insulin antibody levels rose from a geometric mean of 1.9 to 8.2 g/l in contrast to values of 1.4 rising to 16.3 g/l in an age and sex matched historical control group treated from diagnosis only with twice daily conventional bovine isophane insulin. Lipoatrophy at injection sites developed in three (9%) in the Starter group treated with highly purified bovine isophane compared to 7 (22%) of those on conventional bovine isophane. Insulin dose and diabetic control did not differ between the groups. Starterand Switch groups were subsequently treated with semi-synthetic human isophane insulin for 6 months during which insulin antibody levels fell significantly from a geometric mean of 8.5 to 4.4 g/l (p<0.001). We conclude that bovine insulin purified to less than 1 ppm proinsulin is significantly less immunogenic than its conventional proinsulin contaminated counterpart but even at this level of purity is still more immunogenic than human insulin of equivalent purity.